Radio wave meter



A ril 27, 1926. 1,582,780

- P. T. PLATT RADIO WAVE METER Filed April 6, 1925 Fig. 2.

DIAL METER S lnvenTor.

Paul T. PIGTT byMMJ M Patented Apr. 27, 1926.

UNITED STATES 1,582,780 PATENT OFFICE.

PAUL T. PLATT, OF NORFOLK DOWNS, MASSACEUSETTQ.

RADIO WAVE METER.

Application filed April 0, 1925. Serial 1%. 21,005.

To all whom it may concern Be it known that I, PAUL T. PLATII, a c1t1- zen of the United States, and resident of Norfolk Downs, county of Norfolk, State The invention provides a novel radio wavemeter which is relatively simple in construction, but which is highly efficient in opera tion and by means of which it is possible to .tune a non-oscillating receiving set with -very-great accuracy to any desired wave length within the range of the wavemeter.

The main object of the inventionv is to provide a radio wavemeter employlng a single three-electrode vacuum tube which in o eration is entirely silent of itself, 'butw 'ch oscillates at audio frequency, and

oscillations are produced by reason of thefact that the circuit action causes the grid 7 causes to be radiated a radio frequency wave modulated by an audio frequency wave that can -be. picked up on" a non-oscillating receiver, an d which produces a tone which is .pure 1n character and which 1s very easy to tune in sharply.

A. device embodying my invention comprises an oscillating three-electrodevacuum tube, means to. tune the associated circuit to any desired wave length within 'the range of the instrument, said circuit being of sucha design that a radio frequency wave is.

produced and radiated. Audio frequency of the vacuum tube to choke periodically. this blocking action causing periodic interrupti'ons in the radio frequency oscillations which are inaudible in themselves, dividing them into groups of oscillations occurring at much lower andaudible frequencies, and therebycausing a radio frequency signal of low power modulated by an audio frequency -to be radiated, which signal can be picked up on a non-oscillating receiving'set.

In order to give an understanding of the invention I have illustrated herein a wiring diagram for one embodiment thereof after which the novel features will be pointed out in the appended claim.

Fig. 1 is a wiring diagram illustrating the principle of the invention;

Fig. 2'shows a part of a calibration sheet. In the drawings 1, 2 and 3 indicates the filament, grid and plate respectively of a thre electrode vacuum tube. The filament is connected to the low voltage or A battery 4; through a filament circuit 5, the latter having the usual rheostat 7 therein.

The high voltage or B battery is indicated at 8, this being connected to the plate through the'plate circuit 9 as usual.

10 indicates the grid circuit.

The main feature of the invention relates to the oscillation of a single tube at audio frequency in a wavemeter circuit, causing an audio frequency signal to be radiated which can be picked up on a non-oscillating receiving set as a pure smooth note, sharply tuned to a predetermined wave length.

The. theory of operation is as follows. A large, double, plate winding specially interconnected, is close-coupled in fixed relation to the tuned grid inductance, and with fila' ment circuit closed and a moderately high B battery potential applied to the plate, there is a. tendency to. violent radio 'freuency oscillation. However, the grid conenser is bridged by a very high resistance grid leak, of such hi h resistance that the grid of the vacuum tu e chokes periodically, thus dividing the high frequency pulsations generated, into groups which occur at audio frequency, resulting in anaudio frequency signal being radiated, which is tuned to the desired wave length by the variable condenser shunting vthe grid inductance.-

The frequency of the audio wave may be varied within moderate limitsby adjustment of the filament rheostat, such audio frequency variation having no effect on the wave length calibrations. On a-given rheostat setting there will be but very little variation in audio frequency at the opposite ends of the wave length scale of'the wavemeter, this being due to the constants and arrangement of the grid and plate circuits, which are such that audio pulsations are freely produced throughout the wave length range ofi say 1,000,000 cycles to an audible one of approximately 100 cycles, or higher as desired.

In the drawings the large double plate winding is shown at Hand the tuned grid inductance with which this plate winding is close coupled is indicated at 12, 13 indicating the variable condenser by which the tuning is effected, said condenser being operated by any usual control.

21 indicates the usualgrid condenser in the grid circuit and 14 is the high resistance grid leak which bridges said condenser.

One use for which this wavemeter is in tended 1s to assist a person 1n tuning his receiving set exactly to any predetermined.

wave length.

In order to use the wavemeter it is necessary to have it calibrated and to employ u calibration curve or list. The calibration of the instrument consists in determining the.

wave length values corresponding to the various settings of the variable condenser, and which information must be.obtained from a standard source before the wavemeter can be used as such.

I have shown in Fig. 2 a partial list of hypothetical calibration adjustments, the figuresunder the column labeled Dial indicating the reading by dial divisions for the variable condenser, and the figures in the column labeled Meters indicating the corresponding wave length. According to this calibration, if the variable condenser is setat 37 the vacuum tube produces radio" frequency oscillations tuned to 300 meters wave length; ifthe variable'condenser is set at 38, the wave length of the emitted signal will be 306 meters; a settingof the variable-condenser at 39 will cause an audio radiation tuned to 312 meters, etc.

Assuming that the operator desires to set his receiving set for the reception of a broadcast on a 306 meter wave length, he will then adjust the variable condenser of the wavemeter to indicate 38 and when the filament circuit is closed through the rheostat the vacuum tube of the wavemeter will cause radio oscillation-s to be radiated tuned to 306 meter wave length. Y

The grid-choking action of the tube produces'a radio frequency wave tuned to 306 meters which is modulated by audio frequency and may be readily picked up by the non-oscillating receiver and which comes in as a pure smooth tone.

operation the operator will tune his receiving set to the wavemeter, this being done by adjusting the controls of the receiving set until the wavemeter signal comes in clear and strong, and at maximum intensity. This can be readily done because ofv the smooth strong character of the audio frequency note.

The operator then knows that his .set is turned exactly for the reception of radio transmission on a wave length of 306 meters. The wavemeter is then shut oif and the receiving set is in condition to receive any broadcast which may be coming in on the 306 meter wave length. I

The wavemeter may also beused for ascertaining the wave length of any broad" cast which has been picked up by the receiving set.- The-wavemeter will be put in operation and its variable condenser rotated until the audio frequency wave generated by the wavemeter is distinctly heard together with the broadcast, after which a reading is taken of the wavemeters condenser setting. This method will give accuracy to within a meter or two, and if greater accuracy is desired, the filament rheostat of the wavemeter may be adjusted so that straight radio frequency oscillations are produced, after which a .zero beat adjustment on the broadcast stations carrier wave can be made, and from this more accurate information, the exact wave length determined.

I claim:

A radiowavemeter, said wavemeter comprising a single oscillating vacuum tube with filament, grid and plate circuits therefor, a two-section winding in the plate circuit, said sections being connected at their outer ends, a tuned inductance in the grid circuit situated between the inner ends of the two sections of the winding in the plate circuit, a grid condenser in the grid circuit and a highresistance grid leak bridging said grid condenser, whereby a. periodic grid-choking action is produced which causes the radio-frequency oscillations to be broken into groups occurring at audio frequency over a wave length band of at least 188 to 555 meters.

4 In testimony whereof, I have signed my name to this specification. In uslngthe devlce the wavemeter may conveniently be placed from 1 to 10 feet PAUL T. PLATT. 

